Concentration of methionine in amino acid mixtures



Patented Feb. 3, 1953 UNITED STATES PATENT OFFICE CONCENTRATION OF METHIONINE IN AlWINO ACID MIXTURES Robert A. .Noll, Newport, Ky., and orville D.

Frampton, Wyoming, Ohio, assignors to National Distillers Products Corporation, a corporation of Virginia No Drawing. Application September 27,1950, Serial: No. 187,150v

2 Claims;

used for hydrolyzation. After suitably, filtering the. solution to remove. therefrom humin and other impurities, the mineral acid is removed by either, distillation or precipitation and the free amino group. is liberated by suitable neutralization. From. this mixtureuof amino acids, glutamic acid may be separated and recovered.

The separation of glutamic acidirom the, mixture. of amino acids may beobtained in any number of. ways conventionally known. It is preferred however to obtainthe same in accordance Withthe procedure described in copending applicationseriallio. 52,146, fi1ed September 30, 1948. As there shown, an aqueous concentrate of the calcium salts of protein hydrolysis derived from amino acids and having a solid content of about 50 to 80% by weight, are precipitated with methyl alcohol or a mixture of methyl alcohol and acetone, the latter containing not more than 50% byweight of acetone. The alcohol or alcohol acetone mix is added in amount sufficient to .yield about 65.-95.%1o.f the. alcohol oralcohol acetone mix by weight of the total mixture. of materials. Upon dissolving the separated precipitate, .in water and adjusting the pH of the aqueous solution of the precipitate with sulfuric acid to about a. pH of 3.2, calcium sulphateis precipitated with a. minimum of occlusion of glutamic, acid and upon removal of the calcium sulphate and con.- centrating the resultant aqueous solution to a solids content. of about. -65% by weight, the

glutamic acid is obtained in substantially free.

form. Alternatively, the protein hydrol-ysate may be processed in some conventional manner to produce monosodium glutamate. however, where glutamic acid or a glutamate are separated from a protein hydrolysate product a considerable quantity. of amino acids-are obtained.

In. any case,

hydrolysates resulting from the'processing'of distillers, dried grains to produce monosodium glutamate or free glutamic acid possess a relatively large content of methionine, which as'such, or in the form of a concentrate, may he used-to correct a naturally occurring deficiency in many poultry and livestock feed mixtures.

One object of the invention comprises, among others, the recovery of methionine or of a methionine concentrate from the residual hydrolysate product derived in the processing of distillers dried grains to. produce and separate therefrom glutamic acid or glutamate.

In accordance with the invention a residual hydrolysate material, obtained in the glutamic compound separation from protein hydrolysatesx is reacted while at a solids concentrationof, about l-5% by weight, with cuprous chloride at :a pH

be separated by filtration leaving free methioninein the solution. Methionine may be, as: such, recovered from said solution though inmost cases it suffices to obtain asuitable concentrate.

When proceeding, in accordance with the in? vention most of the copper not. converted into the. methionine cuprous chloride complex. remains in solution, either as cuprous chloride or as a soluble copper salt of the other amino, acids present in the hydrolysate. The above mentioned.

reactioneonditions are critical as otherwise the cuprous chloride methionine complex. may not be necessarily obtained in the form of, a precipitate.

and may thus be lost. Any impurities that, may

be. present in the methionine cuprous chloride, complex after its separation. from. its mother.

liquor may be removed by washing. andpare primarily due to adhering mother. liquor.

Within the preferred embodiment of the invention a pH of about 4, a solids concentrationof about 3% by weight and amounts of cuprous. chloride sufiicient to yield about 0.5 mol equivalents of copper for each mol equivalent of nitrogen in the. hydrolysatev treated are recommended;

As herein indicated, a suitable protein mate rial that may be used in accordance with the invention is, for example, that conventionally termed distillers dry grain. Such distillers dry grain is the residual product resulting from the starch to alcohol fermentation of grains. It is not intended, however, to limit the process to the use of such material and other suitable proteins or their hydrolysates may be used when containing methionine material as a component thereof.

A convenient source for a suitable hydrolysate that is particularly well adapted to the practice of the process in the instant invention is, for instance, that furnished as hereinabove indicated, in the calcium glutamate precipitation with methyl alcohol of a protein hydrolysate as described in the copending application, Serial No. 52,146, filed September 30, 1948. As hereinabove mentioned and as there disclosed, a suitable hydrolysate is admixed under certain specific conditions with lime slurry and thereafter methanol is added, resulting in the precipitation of calcium glutamate. This methanol filtrate is first freed from its methanol content by distillation and concentrated to the desired solids content. The concentrate thusly obtained may then be treated directly with the cuprous chloride as herein set forth. Alternatively, it is in some cases desirable,

particularly where relatively large quantities of methionine are present, to first permit the concentrated filtrate to remain quiescent for a period of time to thereby obtain, by quiescent crystallization, a portion of some of the methionine in the resultant crystal crop. The mother liquor of this crystallization is then treated with the cuprous chloride in accordance with the invention.

Instead of adding cuprous chloride to the residual hydrolysate to be treated in accordance with the invention, it is possible and in many cases of advantage, to prepare the cuprous chloride essentially in situ, such as by adding to the hydrolysate cuprous oxide and concentrated hydrochloric acid.

The following examples are furnished by way of illustration but not of limitation:

Example I A suitable kettle, preferably adapted to be operated at both atmospheric and above atmospheric pressure, was charged with about 100 pounds of distillers dried grains containing about 8% moisture. The grain analyzed about 4.2% nitrogen and a calculated glutamic acid content of 5.1

About 392 pounds of a mixed acid composed of about 41 pounds of hydrochloric acid (calculated anhydrous), 16.8 pounds of sulfuric acid (calculated anhydrous) and 334.2 pounds of water were used. The kettle charge was refluxed for about 2 hours at atmospheric pressure, and the furfural formed during this operation distilled off. Thereafter, actual hydrolyzation was efiected by closing the kettle and heating the contents for about 4 hours at a temperature of about 130 C., whereupon the kettle contents were cooled and filtered for the removal of humins. The filtered acid hydrolysate (about 507 pounds) was then subjected to vacuum distillation at a temperature of about 60 C. for the removal of hydrochloric acid. About 38 pounds of hydrochloric acid (calc-ulated anhydrous) were contained in the distillate and were recoverable therefrom.

The concentrated hydrolysate (about 62.5 pounds) containing residual hydrochloric acid of about 2.1% (calculated anhydrous), was then neutralized to pH 7 with lime slurry with cooling and stirring. The resultant calcium sulfate precipitate was then removed by filtration. The resultant filtrate (about 308 pounds) containing about 4.7 pounds glutamic acid in the form of its calcium salt, was then subjected to vacuum concentration at a temperature of about 60 C. or less, down to about 75.4 pounds, having at that point a solids content of about 45.3 pounds (including the calcium glutamate).

To this concentrate was then added about 279 pounds of absolute methanol, with stirring, resulting in a final methanol concentration of about of the total methanol and water present.

The calcium glutamate precipitated upon the addition of the methanol was then removed by filtration and the filter cake washed with about Example II 250 litres of a methanol filtrate obtained, for instance, as specified in Example I, and containing about 0.635 kg. methionine and 57.3 kg. solids was concentrated to 61.5% by weight solids and stored for 40 hours. The crystal crop obtained contained about 60% by weight of the original methionine in a purity of about 3.5%. The mother liquor (80 litres) was then treated with 9.8 litres of concentrated hydrochloric acid and 18.5 kg. cuprous oxide and warmed for 2 hours on the water bath. The mixture had a pH of about 4 and was filtered and diluted with 350 litres of water and litres of methanol. The resulting precipitate was then separated by centrifuging. The precipitate waswashed with water and thereafter decomposed with hydrogen sulfide and filtered. The filtrate contained 16.2% of the original methionine in a purity of 7.2%. Combining the two methionine concentrates would give a yield of 76% and a purity of 3.9%. The original methionine purity is 1.1%.

Though the foregoing experiment sets forth a pre-crystallization of the first concentrate, it is possible to directly treat the methanol filtrate with cuprous chloride provided the same has the specified solids content of from 15% and is at the pH of 3-4.5. It is also possible, and in many,

cases, better yields are obtained depending upon circumstances, to dispense with the use of methanol. J

We claim:

1. In the process of recovering amino acids from protein containing material which comprises hydrolyzing such material with a hydrolyzing acid, thereby producing a, mixture of amino acids, thereafter selectively separating the glutamic acid from such mixture, thereby producing a residue of the remaining amino acids, the improved method of concentrating methionine from such'residue comprising contacting such residue at a solids concentration of from l-5% and at a pH of from 3-4.5 with cuprous chloride in amount sufficient to yield 0.25 to 1.0 mol of copper for each mol of nitrogen present, thereby producing a copper methionine precipitate, separating such precipitate and recovering methionine therefrom.

2. Improvement in accordance with claim 1 in which said solid concentration is about 3%, said pH is about 4 and said cuprous chloride is added in amount sufficient to yield about 0.5 mol of cop- 5 6 per for each mol of nitrogen present in said UNITED STATES PATENTS resldue' Number Name Date ROBERT A NOLL. 2,376,186 Rapkine May 15, 1945 Holloway et a1 Jan. 14, 5 2,462,124 Neuberg et a1 Feb. 22, 1949 OTHER REFERENCES REFERENCES CITED P1r1e: Blochem. J v01. 26, pp. 1270-1274 (1932).

The following references are of record in the Cunningham et a1: Chem Abstr V01 31 c01- file of this patent: 10 4357 (1937). w 1 

1. IN THE PROCESS OF RECOVERING AMINO ACIDS FROM PROTEIN CONTAINING MATERIAL WHICH COMPRISES HYDROLYZING SUCH MATERIAL WITH A HYDROLYZING ACID, THEREBY PRODUCING A MIXTURE OF AMINO ACIDS, THEREAFTER SELECTIVELY SEPARATING THE GLUTAMIC ACID FROM SUCH MIXTURE, THEREBY PRODUCING A RESIDUE OF THE REMAINING AMINO ACIDS, THE IMPROVED METHOD OF CONCENTRATING METHIONINE FROM SUCH RESIDUE COMPRISING CONTACTING SUCH RESIDUE AT A SOLIDS CONCENTRATION OF FROM 1-5% AND AT A PH OF FROM 3-45 WITH CUPROUS CHLORIDE IN AMOUNT SUFFICIENT TO YIELD 0.25 TO 1.0 MOL OF COPPER FOR EACH MOL OF NITROGEN PRESENT, THEREBY PRODUCING A COPPER METHIONINE PRECIPITATE, SEPARATING SUCH PRECIPITATE AND RECOVERING METHIONINE THEREFROM. 